Method of preparing supported metallocene catalyst and method of preparing polypropylene using catalyst prepared thereby

ABSTRACT

Provided are a method of preparing a supported metallocene catalyst, and a method of preparing polypropylene using the catalyst prepared thereby. According to the present invention, provided is a supported metallocene catalyst capable of preparing an isotactic polypropylene polymer having a low xylene soluble content while having excellent catalytic activity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national phase entry under 35 U.S.C. § 371 ofInternational Application No. PCT/KR2018/015933 filed Dec. 14, 2018,which claims priority from Korean Patent Application No. 10-2017-0180263filed Dec. 26, 2017, and Korean Patent Application No. 10-2018-0161297filed Dec. 13, 2018, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION (a) Field of the Invention

The present invention relates to a method of preparing a supportedmetallocene catalyst, and a method of preparing polypropylene using thecatalyst prepared thereby.

(b) Description of the Related Art

Catalysts for olefin polymerization may be classified into Ziegler-Nattacatalysts and metallocene catalysts, and these two catalysts have beendeveloped in compliance with their characteristics.

A Ziegler-Natta catalyst has been widely applied to existing commercialprocesses since it was developed in the 1950's. However, since theZiegler-Natta catalyst is a multi-active site catalyst in which aplurality of active sites are mixed, a polymer prepared by using thesame has a broad molecular weight distribution. Also, since comonomercompositional distribution is not uniform, it has a limitation to securethe desired physical properties. In particular, since polypropyleneprepared using Ziegler-Natta catalysts has a high xylene soluble content(e.g., more than 5% by weight), there is a limitation in that it isdifficult to obtain polypropylene having a low melting point (Tm) whenZiegler-Natta catalysts are used.

The metallocene catalyst includes a combination of a main catalyst, ofwhich main component is a transition metal compound, and a cocatalyst,of which main component is aluminum. Such a catalyst is a single-sitecatalyst which is a homogeneous complex catalyst. Therefore, themetallocene catalyst allows preparation of polypropylene having a narrowmolecular weight distribution and a uniform comonomer compositionaldistribution. Further, the metallocene catalyst has characteristicscapable of changing the stereoregularity, copolymerization properties,molecular weight, degree of crystallinity, etc. of polypropylene bychanging a ligand structure and polymerization conditions.

Among them, an ansa-metallocene catalyst is an organometallic catalystincluding two ligands which are linked to each other via a bride group.The bridge group prevents rotation of the ligands and determines theactivity and structure of the metal center. Particularly, in thepolymerization of polypropylene, the ansa-metallocene catalyst may forma polymer having a low xylene soluble content, and thus it isadvantageous in preparing polypropylene having a low melting point.

Meanwhile, during preparation of the ansa-metallocene catalyst, aracemic form and a meso isomer are produced at the same time. Thus, toprepare an isotactic polymer having high crystallinity and melting pointand high specific gravity and mechanical strength, it is required toseparate a metallocene compound of a racemic form with high-purity froma mixture of the meso isomer and the racemic form.

However, the racemic form and meso isomer show no great difference insolubility for a general recrystallization solvent, and thus it is noteasy to separate a pure racemic form.

Accordingly, there is a demand for the development of a method capableof obtaining a metallocene compound of a racemic form with high-purityin a simpler manner than the existing methods.

SUMMARY OF THE INVENTION

The present invention provides a method of preparing a catalystincluding a metallocene compound of a racemic form with high-purity inorder to provide a supported metallocene catalyst which allowspolymerization of a desired isotactic polypropylene having highstereoregularity.

Further, the present invention provides a method of preparingpolypropylene using the supported metallocene catalyst.

According to the present invention, provided is a method of preparing asupported metallocene catalyst, the method including the steps of:

preparing a mixture of a racemic form of the following Chemical Formula1 and a meso isomer of the following Chemical Formula 2;

dissolving the mixture in a solvent including toluene and hexane;

filtering the mixture dissolved in the solvent to remove the solidifiedmeso isomer of Chemical Formula 2; and

removing the solvent from the filtered mixture, and then supporting theresulting product onto a carrier:

in Chemical Formulae 1 and 2,

X¹ and X² are each independently halogen,

R¹ and R^(1′) are each independently an aryl group having 6 to 20 carbonatoms which is substituted with an alkyl group having 1 to 20 carbonatoms,

R², R³, R⁴, R^(2′), R^(3′), and R^(4′) are each independently hydrogen,halogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl grouphaving 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbonatoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl grouphaving 7 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbonatoms,

A is carbon, silicon, or germanium, and

R⁵ and R⁶ are each independently an alkyl group having 1 to 20 carbonatoms.

Further, according to the present invention, provided is a method ofpreparing polypropylene, the method including the step of polymerizingmonomers including propylene in the presence of the supportedmetallocene catalyst.

According to the method of preparing the supported metallocene catalystaccording to the present invention, it is possible to prepare asupported metallocene catalyst including a high-purity racemic form in asimpler manner.

Accordingly, when the supported metallocene catalyst prepared by themethod is used, it is possible to prepare an isotactic polypropylenepolymer having a low xylene soluble content while exhibiting excellentcatalytic activity.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Unless otherwise described throughout the specification, technical termsare to address specific embodiments, and are not intended to limit thepresent invention.

Also, singular forms used herein include plural forms unless they haveexplicitly contrary meanings. Further, the term ‘including’ used hereinspecifies properties, areas, integers, steps, operations, elements,and/or ingredients, but does not exclude the presence or addition ofother properties, areas, integers, steps, operations, elements,ingredients, and/or groups.

As used herein, the term “racemic form” means that the substituents onthe two cyclopentadienyl moieties exist on the opposite side withrespect to the plane containing zirconium and the center of thecyclopentadienyl moieties.

As used herein, the term “meso isomer”, which is a stereoisomer of aracemic form, means that the substituents on the two cyclopentadienylmoieties exist on the same side with respect to the plane containingzirconium (Zr) and the center of the cyclopentadienyl moieties.

According to one embodiment of the present invention, provided is amethod of preparing a supported metallocene catalyst, the methodincluding the steps of:

preparing a mixture of a racemic form of the following Chemical Formula1 and a meso isomer of the following Chemical Formula 2;

dissolving the mixture in a solvent including toluene and hexane;

filtering the mixture dissolved in the solvent to remove the solidifiedmeso isomer of Chemical Formula 2; and

removing the solvent from the filtered mixture, and then supporting theresulting product onto a carrier:

in Chemical Formulae 1 and 2,

X¹ and X² are each independently halogen,

R¹ and R^(1′) are each independently an aryl group having 6 to 20 carbonatoms which is substituted with an alkyl group having 1 to 20 carbonatoms,

R², R³, R⁴, R^(2′), R^(3′), and R^(4′) are each independently hydrogen,halogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl grouphaving 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbonatoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl grouphaving 7 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbonatoms,

A is carbon, silicon, or germanium, and

R⁵ and R⁶ are each independently an alkyl group having 1 to 20 carbonatoms.

The metallocene compound of Chemical Formula 1 has an ansa-metallocenestructure including two indenyl groups as ligands, and includeszirconium (Zr) as a metal atom, thereby exhibiting high catalyticactivity.

Further, since the ligands are substituted by bulky groups (R¹ andR^(1′)), a steric hindrance is provided, and thus formation of themetallocene compound of the meso isomer may be basically preventedduring synthesis of the catalyst. However, it is difficult to inhibitthe formation of the meso isomer below 30 mol %.

However, as explained above, since the metallocene compound of the mesoisomer forms an atatic polypropylene, it is necessary to purify only themetallocene compound of the racemic form with high-purity in order toprepare the isotactic polypropylene.

A basic method of separating the racemic form from the meso isomer is toseparate the racemic form by solidify the racemic form throughrecrystallization using a solubility difference, focusing on the factthat the racemic form generally has poorer solubility than the mesoisomer. However, with regard to the metallocene compound of ChemicalFormula 1, the racemic form and the meso isomer show no great differencein solubility for DCM (dichloromethane) which is generally used as arecrystallization solvent, and therefore, it is not easy to isolate thepure racemic form. Further, a considerable amount of the racemic formalso exists in the filtrate remaining after removing the solidifiedracemic form, and thus there is a problem in that the overall yield islow.

Accordingly, the present inventors have found conditions under which theracemic form shows higher solubility than the meso isomer. Under theseconditions, the mixture of the racemic form and the meso isomer isdissolved (recrystallized) to separate the racemic form in a liquid formand to remove the meso isomer in a solid form, and as a result, theracemic form may be isolated in high purity by purification, therebycompleting the present invention.

Hereafter, the method of preparing the supported metallocene catalyst ofthe present invention will be described in more detail.

First, the metallocene mixture including the racemic form of thefollowing Chemical Formula 1 and the meso isomer of the followingChemical Formula 2 is prepared.

in Chemical Formulae 1 and 2,

X¹ and X² are each independently halogen,

R¹ and R^(1′) are each independently an aryl group having 6 to 20 carbonatoms which is substituted with an alkyl group having 1 to 20 carbonatoms,

R², R³, R⁴, R^(2′), R^(3′), and R^(4′) are each independently hydrogen,halogen, an alkyl group having 1 to 20 carbon atoms, an alkenyl grouphaving 2 to 20 carbon atoms, an alkoxy group having 1 to 20 carbonatoms, an aryl group having 6 to 20 carbon atoms, an alkylaryl grouphaving 7 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbonatoms,

A is carbon, silicon, or germanium, and

R⁵ and R⁶ are each independently an alkyl group having 1 to 20 carbonatoms.

According to one embodiment of the present invention, in ChemicalFormulae 1 and 2, X¹ and X² may be each independently halogen, andpreferably, Cl.

In Chemical Formulae 1 and 2, R¹ and R^(1′) may be each independently anaryl group having 6 to 20 carbon atoms which is substituted with analkyl group having 1 to 20 carbon atoms, preferably a phenyl groupsubstituted with tert-butyl, and more preferably, a 4-tert-butyl phenylgroup.

In Chemical Formulae 1 and 2, R², R³, R⁴, R^(2′), R^(3′), and R^(4′) maybe each independently preferably hydrogen or an alkyl group having 1 to20 carbon atoms, and more preferably, hydrogen.

In Chemical Formulae 1 and 2, A may be carbon, silicon, or germanium,and preferably silicon.

In Chemical Formulae 1 and 2, R⁵ and R⁶ may be each independently analkyl group having 1 to 20 carbon atoms, and preferably a methyl group.

According to one embodiment of the present invention, a representativeexample of the racemic form compound of Chemical Formula 1 is asfollows:

A representative example of the meso isomer compound of Chemical Formula2 is as follows:

The metallocene mixture including the racemic form of Chemical Formula 1and the meso isomer of Chemical Formula 2 may be prepared by thefollowing method, and the present invention is not limited thereto.

First, a compound of the following Chemical Formula 1-2 is reacted witha compound of the following Chemical Formula 1-3 to prepare a compoundof Chemical Formula 1-4. This reaction may be performed using alkyllithium (e.g., n-butyl lithium) as a catalyst at a temperature of −200°C. to 0° C.

Next, the compound of the following Chemical Formula 1-4 is reacted witha compound of the following Chemical Formula 1-5 to prepare a compoundof Chemical Formula 1-6. This reaction may be performed using alkyllithium (e.g., n-butyl lithium) as a catalyst at a temperature of −200°C. to 0° C. At this time, an organic layer is separated from theproduct, and after vacuum-drying the separated organic layer, an excessof the reactant is preferably removed therefrom.

Next, the compound of the following Chemical Formula 1-6 is reacted witha compound of Chemical Formula 1-7. Through this reaction, a metallocenecompound may be obtained in a mixture form of the racemic form ofChemical Formula 1 and the meso isomer of Chemical Formula 2.

in Chemical Formulae 1-2 to 1-7, X¹, X², A, R¹, R^(1′), R², R³, R⁴,R^(2′), R^(3′), R^(4′), R⁵ and R⁶ are defined as in Chemical Formulae 1and 2.

A molar ratio (rac:meso) of the racemic form of Chemical Formula 1 tothe meso isomer of Chemical Formula 2 in the mixture may be, but varydepending on the reaction conditions, about 1:1 to about 3:1, and it isdifficult to increase the molar ratio of the racemic form more than theabove in the synthesis step.

Next, the mixture is dissolved in a solvent including toluene andhexane.

A weight ratio of toluene and hexane may be 1:0.01 to 1:100, 1:0.1 to1:10, or 1:0.5 to 1:2.

Further, a dissolution temperature may be in the range of −78° C. orhigher, −30° C. or higher, or −25° C. or higher, and 70° C. or lower,60° C. or lower, or 25° C. or lower, preferably −30° C. or higher and70° C. or lower, preferably −25° C. or higher and 70° C. or lower, andmore preferably −25° C. or higher and 60° C. When the dissolutiontemperature is within the above range, the molar ratio of the racemicform to the meso isomer may be further increased.

Further, the dissolution may be performed for 1 hr or longer, 24 hr orlonger, or 48 hr or longer, and 128 hr or shorter, 96 or shorter, 72 orshorter, or 60 or shorter.

Further, concentrations of toluene and hexane may be each independently0.05 M or more, 0.1 M or more, or 0.2 M or more, and 2.0 M or less, 1.5M or less, 1.0 M or less, or 0.5 M or less.

Further, the mixture may be dissolved by mixing the mixture with tolueneand hexane, sequentially or simultaneously.

When the mixture is sequentially dissolved in toluene and hexane,toluene is first added to the mixture, and sequentially, hexane is addedthereto such that the mixture may be dissolved at a temperature lowerthan the dissolution temperature of toluene. As described, bysimultaneously applying the temperature drop method and the solventusage method of using a dissolution difference between solvents, inwhich toluene is first added to dissolve the mixture, and then at thelower temperature, hexane is added to dissolve the mixture, it ispossible to expect a recrystallization effect of further increasing themolar ratio of the racemic form.

According to one embodiment of the present invention, toluene is firstadded to dissolve the mixture at a temperature of 30° C. to 70° C., or40 to 70° C. for 0.1 hr to 3 hr, and then hexane is added to dissolvethe mixture at a temperature of −30° C. to 30° C., or −25° C. to 25° C.for 6 hr to 96 hr.

According to one embodiment of the present invention, when the weightratio of the toluene and hexane solvents, and the dissolutiontemperature and time satisfy the above range, the solubility of theracemic form relative to the meso isomer is further increased, therebyobtaining the racemic form with higher purity.

In other words, when the mixture is dissolved under the aboveconditions, the racemic form exhibits much higher solubility than themeso isomer. As a result, in the mixture which is dissolved in thesolvent including toluene and hexane, the molar ratio (rac:meso) of theracemic form to the meso isomer may be 7 or more, 8 or more, or 9 ormore, and 30 or less, 25 or less, 20 or less, or 18 or less, and thecontent of the racemic form may be greatly increased, and the mesoisomer having relatively low solubility may be precipitated in a solidform.

Further, according to one embodiment of the present invention, the stepof dissolving the mixture of racemic form/meso isomer in the solventincluding toluene and hexane may be performed twice or more. When thedissolving step is performed twice or more, the molar ratio of theracemic form to the meso isomer may be further increased in the seconddissolution step, because the molar ratio of the racemic form to themeso isomer has been already increased in the previous dissolution step.

Next, the mixture dissolved in the solvent is filtered using a filter,etc., thereby removing the solidified meso isomer of Chemical Formula 2.From the mixture from which the solidified meso isomer is removed, thesolvent including toluene and hexane is removed by distillation underreduced pressure, thereby obtaining a metallocene catalyst having a muchhigher content of the racemic form of Chemical Formula 1. Thereafter,the metallocene catalyst having a higher content of the racemic form isdissolved in a non-polar solvent such as hexane, heptane, or pentane,and impurity is additionally removed by filtration using a filter, etc.,thereby finally obtaining a high-purity racemic form.

Subsequently, the metallocene catalyst is supported on a carrieraccording to a common supporting method.

As the carrier, a carrier containing a hydroxyl group on its surface maybe used. Specifically, the carrier may be a carrier containing a highlyreactive hydroxyl group or siloxane group, of which the surface is driedand removed of moisture. For non-limiting example, the carrier includesilica, silica-alumina, and silica-magnesia dried at a high temperature.The carrier may include oxides such as Na₂O, carbonates such as K₂CO₃,sulfates such as BaSO₄, and nitrate components such as Mg(NO₃)₂.

According to one embodiment of the present invention, the supportedmetallocene catalyst may further include one or more cocatalystsselected from the group consisting of compounds represented by thefollowing Chemical Formulae 3 to 5, in addition to the metallocenecompound:—[Al(R⁷)—O]_(c)—  [Chemical Formula 3]

in Chemical Formula 3,

c is an integer of 2 or more,

R⁷ is each independently halogen, a hydrocarbyl group having 1 to 20carbon atoms, or a halogen-substituted hydrocarbyl group having 1 to 20carbon atoms;D(R⁸)₃  [Chemical Formula 4]

in Chemical Formula 4,

D is aluminum or boron,

R⁸ is each independently halogen, a hydrocarbyl group having 1 to 20carbon atoms, or a halogen-substituted hydrocarbyl group having 1 to 20carbon atoms;[L-H]⁺[Q(E)₄]⁻  [Chemical Formula 5]

in Chemical Formula 5,

L is a neutral Lewis base,

[L-H]⁺ is a Bronsted acid,

Q is boron or aluminum in the oxidation state of +3, and

E is each independently an aryl group having 6 to 20 carbon atoms or analkyl group having 1 to 20 carbon atoms, in which one or more hydrogenatoms are substituted or unsubstituted with halogen, a hydrocarbyl grouphaving 1 to 20 carbon atoms, an alkoxy or phenoxy functional group.

Specifically, the compound represented by Chemical Formula 3 may includealkylaluminoxane such as methylaluminoxane, ethylaluminoxane,butylaluminoxane, isobutylaluminoxane, etc. Further, the compoundrepresented by Chemical Formula 3 may include modified methylaluminoxane(MMAO) obtained by replacing a part of methyl groups of themethylaluminoxane by other alkyl groups. For example, the modifiedmethylaluminoxane may be a compound obtained by replacing 40 mol % orless, or 5 mol % to 35 mol % of methyl groups of the methylaluminoxaneby a linear or branched alkyl group having 3 to 10 carbon atoms.Examples of the modified methylaluminoxane commercially available mayinclude MMAO-12, MMAO-3A, MMAO-7, etc.

Further, the compound represented by Chemical Formula 4 may includetrimethylaluminum, triethylaluminum, triisobutylaluminum,tripropylaluminum, tributylaluminum, dimethylchloroaluminum,dimethylisobutylaluminum, dimethylethylaluminum, diethylchloroaluminum,triisopropylaluminum, triisobutylaluminum, tri-s-butylaluminum,tricyclopentylaluminum, tripentylaluminum, triisopentylaluminum,trihexylaluminum, ethyldimethylaluminum, methyldiethylaluminum,triphenylaluminum, tri-p-tolylaluminum, dimethylaluminummethoxide,dimethylaluminumethoxide, trimethylboron, triethylboron,triisobutylboron, tripropylboron, tributylboron, etc.

Further, the compound represented by Chemical Formula 5 may includetriethylammonium tetraphenylboron, tributylammonium tetraphenylboron,trimethylammonium tetraphenylboron, tripropylammonium tetraphenylboron,trimethylammonium tetra(p-tolyl)boron, tripropylammoniumtetra(p-tolyl)boron, triethylammonium tetra(o,p-dimethylphenyl)boron,trimethylammonium tetra(o,p-dimethylphenyl)boron, tributylammoniumtetra(p-trifluoromethylphenyl)boron, trimethylammoniumtetra(p-trifluoromethylphenyl)boron, tributylammoniumtetrapentafluorophenylboron, N,N-diethylanilinium tetraphenyl boron,N,N-diethylanilinium tetraphenylboron, N,N-diethylaniliniumtetrapentafluorophenylboron, diethylammoniumtetrapentafluorophenylboron, triphenylphosphonium tetraphenylboron,trimethylphosphonium tetraphenylboron, triethylammoniumtetraphenylaluminum, tributylammonium tetraphenylaluminum,trimethylammonium tetraphenylaluminum, tripropylammoniumtetraphenylaluminum, trimethylammonium tetra(p-tolyl)aluminum,tripropylammonium tetra(p-tolyl)aluminum, triethylammoniumtetra(o,p-dimethylphenyl)aluminum, tributylammoniumtetra(p-trifluoromethylphenyl)aluminum, trimethylammoniumtetra(p-trifluoromethylphenyl)aluminum, tributylammoniumtetrapentafluorophenylaluminum, N,N-diethylaniliniumtetraphenylaluminum, N,N-diethylanilinium tetraphenylaluminum,N,N-diethylanilinium tetrapentafluorophenylaluminum, diethylammoniumtetrapentafluorophenylaluminum, triphenylphosphoniumtetraphenylaluminum, trimethylphosphonium tetraphenylaluminum,triphenylcarbonium tetraphenylboron, triphenylcarboniumtetraphenylaluminum, triphenylcarboniumtetra(p-trifluoromethylphenyl)boron, triphenylcarboniumtetrapentafluorophenylboron, etc.

Specifically, as the cocatalyst, one or more compounds selected from thegroup consisting of trimethyl aluminum, triethyl aluminum, triisopropylaluminum, triisobutyl aluminum, ethylaluminum sesquichloride,diethylaluminum chloride, ethyl aluminum dichloride, methylaluminoxane,and modified methylaluminoxane may be preferably applied.

Further, the content of the cocatalyst may be determined by consideringcatalytic activity, etc. According to one embodiment of the presentinvention, the cocatalyst may be included at a molar ratio of 1:1 to1:10000, 1:1 to 1:5000, or 1:1 to 1:3000 with respect to the totalweight of the metallocene compound.

Meanwhile, in this case, the supported metallocene catalyst may beprepared, in any order, by first supporting the cocatalyst onto thecarrier, and then supporting the metallocene compound onto thecocatalyst-supported carrier, or by first supporting the metallocenecompound onto the carrier, and then supporting the cocatalyst thereto.

In the preparation of the supported catalyst, a hydrocarbon solvent suchas pentane, hexane, heptane, etc., or an aromatic solvent such asbenzene, toluene, etc. may be used.

According to the preparation method as described, the content of themetallocene compound of the racemic form in the catalyst may beincreased in a simpler manner, and when the supported metallocenecatalyst prepared by supporting the same onto the carrier is used, it ispossible to obtain a high-quality isotactic propylene polymer.

Meanwhile, according to another embodiment of the present invention,provided is a method of preparing polypropylene, the method includingthe step of polymerizing monomers including propylene in the presence ofthe supported metallocene catalyst prepared by the above preparationmethod.

The method of preparing polypropylene may be performed in the presenceof the above-described supported metallocene catalyst using monomersincluding propylene as a raw material by applying a common device andcontact technology.

For non-limiting example, the method of preparing polypropylene may beperformed by homopolymerization of propylene or random polymerization ofpropylene and a comonomer using a continuous slurry polymerizationreactor, a loop slurry reactor, a gas phase reactor, or a solutionreactor. The comonomer may include ethylene, 1-butene, 1-pentene,4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene,1-dodecene, 1-tetradecene, 1-hexadecene, 1-eicosene, etc.

In the preparation method, the supported metallocene catalyst may beused in a state of being dissolved or diluted in a solvent such aspentane, hexane, heptane, nonane, decane, toluene, benzene,dichloromethane, chlorobenzene, etc.

Further, the method of preparing polypropylene may be performed at atemperature of 20° C. to 500° C. or 20° C. to 200° C. and a pressure of1 kgf/cm² to 100 kgf/cm², or 1 kgf/cm² to 70 kgf/cm² for 1 hr to 24 hr,or 1 hr to 10 hr. As needed, the polymerization may be performed underconditions in which hydrogen is added thereto or not.

Further, the preparation method may be appropriately applied to thepreparation of desired isotactic polypropylene.

Hereinafter, preferred examples will be provided for betterunderstanding of the present invention. However, the following examplesare provided only for illustrating the present invention, and thepresent invention is not limited thereby.

EXAMPLE

Preparation of Crude Mixture of Racemic Form and Meso Isomer

Synthesis Example 1 Preparation of(4-(4-(tert-butyl)phenyl)-2-isopropyl-1H-inden-1-yl)dimethyl(2-methyl-4-phenyl-1H-inden-1-yl)silane

2-iPr-4-tBuPhIndene (1 equiv) was dissolved in toluene/THF (10/1, 0.5M), and then n-BuLi (1.05 eq) was slowly added thereto at −25° C.,followed by stirring at room temperature for 3 hr. Thereafter,dichlorodimethyl silane (1.05 eq) was added at −10° C., followed bystirring at room temperature overnight. In another reactor,2-Me-4-tBuPhIndene (1 eq) was dissolved in toluene/THF (5/1, 0.7 M), andthen n-BuLi (1.05 eq) was slowly added at −25° C., followed by stirringat room temperature for 3 hr. Thereafter, CuCN (2 mol %) was added,followed by stirring for 30 min. Then, the first reactant mono-Sisolution was added, followed by stirring at room temperature overnight.Work-up was performed using water, and then dried to obtain a ligand.

Preparation ofdimethylsilanyl-(4-(4-tert-butylphenyl)phenyl)-2-methyl-1H-inden-1-yl)(4-(4-tert-butylphenyl)phenyl)-2-isoproyl-1H-inden-1-yl)zirconium dichloride (mixture of rac and meso)

The ligand was dissolved in toluene/ether (2/1, 0.53 M), and n-BuLi(2.05 eq) was added thereto at −25° C., followed by stirring at roomtemperature for 5 hr. A slurry of ZrCl₄ (1 eq) in toluene (0.17 M) wasprepared and added to a flask, followed by stirring at room temperatureovernight.

When the reaction was completed, the solvent was vacuum-dried, and DCMwas added again and LiCl was removed through a filter, etc. the filtratewas vacuum-dried to obtain a metallocene compound in the form of amixture of racemic form and meso isomer (rac:meso=2:1, a molar ratio).

¹H NMR (500 MHz, CDCl₃, 7.26 ppm) ofRac-dimethylsilanyl-(4-(4-tert-butylphenyl)phenyl)-2-methyl-1H-inden-1-yl)(4-(4-tert-butylphenyl)phenyl)-2-isoproyl-1H-inden-1-yl)zircoiumdichloride: 0.89 (6H, t), 1.19 (3H, d), 1.34 (9H, s), 1.35 (9H, s), 1.47(3H, d), 1.50 (3H, s), 2.38 (3H, s), 3.20 (1H, m), 6.88 (2H, m), 6.94(2H, d), 7.14 (2H, d), 7.44 (4H, t), 7.52 (4H, d), 7.65 (2H, t)

Example 1

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,and dissolved at 60° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried. After completing the solvent drying, a ratio of rac:mesowas examined by NMR. Further, a ratio of rac:meso in the filter cake wasalso examined.

Example 2

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,and dissolved at 60° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to 25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried. After completing the solvent drying, a ratio of rac:mesowas examined by NMR. Further, a ratio of rac:meso in the filter cake(solid phase) was also examined.

Example 3

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,and dissolved at 40° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried.

To 3.7 g of the mixture thus obtained, 0.52 M toluene was added, anddissolved at 40° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried. After completing the solvent drying, a ratio of rac:mesowas examined by NMR. Further, a ratio of rac:meso in the filter cake wasalso examined.

Example 4

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,and dissolved at 60° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried.

To 3.9 g of the mixture thus obtained, 0.66 M toluene was added, anddissolved at 60° C. for 1 hr. Thereafter, 0.66 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried. After completing the solvent drying, a ratio of rac:mesowas examined by NMR. Further, a ratio of rac:meso in the filter cake wasalso examined.

Example 5

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,and dissolved at 60° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried.

To 3.9 g of the mixture thus obtained, 0.52 M toluene was added, anddissolved at 60° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried. After completing the solvent drying, a ratio of rac:mesowas examined by NMR. Further, a ratio of rac:meso in the filter cake wasalso examined.

Example 6

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,and dissolved at 60° C. for 1 hr. Thereafter, 0.52 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried.

To 3.9 g of the mixture thus obtained, 0.4 M toluene was added, anddissolved at 60° C. for 1 hr. Thereafter, 0.4 M hexane was addedthereto, followed by stirring for 30 min. Then, the temperature wasdecreased to −25° C., and maintained for 72 hr. A supernatant wasobtained by decantation, and a filter cake was separated through afilter. The supernatant and filtrate were collected together andvacuum-dried. After completing the solvent drying, a ratio of rac:mesowas examined by NMR. Further, a ratio of rac:meso in the filter cake wasalso examined.

COMPARATIVE EXAMPLE 1

0.52 M toluene was added to 10 g of the mixture of Synthesis Example 1,followed by stirring for 30 min. Then, the temperature was decreased to−25° C., and maintained for 72 hr. A supernatant was obtained bydecantation, and a filter cake was separated through a filter. Thesupernatant and filtrate were collected together and vacuum-dried. Aftercompleting the solvent drying, a ratio of rac:meso was examined by NMR.Further, a ratio of rac:meso in the filter cake was also examined.

Comparative Example 2

1.0 M DCM was added to 10 g of the mixture of Synthesis Example 1,followed by stirring for 30 min. Then, the temperature was decreased to−25° C., and maintained for 72 hr. A supernatant was obtained bydecantation, and a filter cake was separated through a filter. Thesupernatant and filtrate were collected together and vacuum-dried. Aftercompleting the solvent drying, a ratio of rac:meso was examined by NMR.Further, a ratio of rac:meso in the filter cake was also examined.

Recrystallization conditions and changes in the ratio of rac:meso inExamples and Comparative Examples are shown in Table 1 below.

TABLE 1 Molar ratio of racemic form to meso isomer (rac:meso)Recrystallization conditions Solid phase Liquid phase Number Beforeafter after Yield No. Solvent Temperature of times recrystallizationrecrystallization recrystallization (%) Example 1 Tol/Hex 60° C./−25° C.1 2 2 7 39 Example 2 Tol/Hex 60° C./25° C. 1 2 1 17 35 Example 3 Tol/Hex40° C./−25° C. 2 2 0.6 11 29 Example 4 Tol/Hex 60° C./−25° C. 2 2 1 9 25Example 5 Tol/Hex 60° C./−25° C. 2 2 0.2 16 27 Example 6 Tol/Hex 60°C./−25° C. 2 2 1.8 8 35 Comparative Toluene −25° C. 1 2 2 2.1 40 Example1 Comparative DCM −25° C. 1 2 4 1.6 10 Example 2

(In Table 1, the yield means a total yield from a synthesis startingmaterial (indene derivative).)

Referring to Table 1, Examples 1 to 6, in which recrystallization wasperformed using the mixed solvent of toluene/hexane, showed theremarkably increased molar ratio of the racemic form in the filtrateafter recrystallization, i.e., in the liquid-phase, as compared withthat before recrystallization, and also showed the high yield.

Comparative Example 1, in which recrystallization was performed usingthe toluene solvent alone, showed the slightly high yield, as comparedwith Examples, but showed a change in the molar ratio of the racemicform from 2 to 2.1, indicating little effect of increasing the racemicform. Comparative Example 2, in which the racemic form was separated ina solid phase using the DCM solvent, showed an increase in the molarratio of the solid-phase racemic form from 2 to 4, but showed the verylow yield of 10%.

Preparation Example of Supported Catalyst

Supported catalysts were prepared using each of the catalysts obtainedin Examples, as follows.

Preparation Example 1

10 g of silica and 10 wt % of methylaluminoxane (67 g) were put in a 300mL reactor, and allowed to react at 90° C. for 24 hr. Afterprecipitation, the supernatant was removed, and the precipitate waswashed with toluene twice. The metallocene catalyst (580 mg) of Example1 was diluted with toluene, which was then added to the reactor, andallowed to react at 70° C. for 5 hr. When precipitation was completedafter reaction, the supernatant was removed, and the remaining reactionproduct was washed with toluene, and then washed with hexane, andvacuum-dried to obtain 15 g of a silica supported metallocene catalystin a solid particle shape.

Preparation Example 2

A supported metallocene catalyst was prepared in the same manner as inPreparation Example 1, except that the metallocene catalyst of Example 6was used.

Preparation Example 3

A supported metallocene catalyst was prepared in the same manner as inPreparation Example 1, except that the metallocene catalyst of Example 3was used.

Preparation Example 4

A supported metallocene catalyst was prepared in the same manner as inPreparation Example 1, except that the metallocene catalyst of Example 5was used.

Comparative Preparation Example 1

A supported metallocene catalyst was prepared in the same manner as inPreparation Example 1, except that the metallocene catalyst obtained ina solid phase in Comparative Example 2 was used.

Polymerization Examples of Propylene Examples 7 to 10 and ComparativeExample 3

A 2 L stainless reactor was vacuum-dried at 65° C., and then cooled. 3mmol of triethylaluminum was injected at room temperature, and 1500 ppmof hydrogen was injected, and then 770 g of propylene was injectedthereto, followed by stirring for 5 min. 30 mg of each of the supportedmetallocene catalysts obtained in Preparation Examples 1 to 4 andComparative Preparation Example 1 was injected into the reactor undernitrogen pressure. Thereafter, the reactor temperature was slowly raisedto 70° C., and polymerization was allowed for 1 hr. After completing thereaction, unreacted propylene was vented.

Experimental Example

The polypropylenes prepared in Polymerization Examples were measured forthe following physical properties, and the results are shown in Table 2below.

(1) Catalytic activity: a ratio of the weight (kg) of the producedpolymer to the amount of the used catalyst (g of catalyst) wascalculated, based on unit time (h).

(2) Xylene solubles (XS) of polymer:xylene was added to the sample, andpretreated by heating at 135° C. for 1 hr and cooling for 30 min. Thepretreated sample was measured in OmniSec (FIPA manufactured by ViscotekCorp.) at a flow rate of 1 ml/min, and a refractive index peak area wascalculated.

TABLE 2 Used catalyst Molar ratio of racemic form to Polymerization mesoactivity Xylene Supported isomer (kg-PP/ solubles catalyst (rac:meso)g-cat · hr) (XS) (%) Example 7 Preparation 7 3.0 1.45 Example 1 Example8 Preparation 8 6.3 1.1 Example 2 Example 9 Preparation 11 7.2 0.7Example 3 Example 10 Preparation 16 10.2 0.7 Example 4 ComparativeComparative 4 1.5 8 Example 3 Preparation Example 1

Referring to Table 2, according to the preparation method of the presentinvention, the supported metallocene catalyst having a high molar ratioof the racemic form were obtained. It was confirmed that when thesupported metallocene catalyst obtained by the preparation method wasused to polymerize polypropylene, polypropylene having low xylenesolubles were prepared with high activity.

However, the catalyst of Comparative Preparation Example 1 had the highcontent of the meso isomer, and thus when the catalyst of ComparativePreparation Example 1 was used to polymerize polypropylene, thecatalytic activity was low, and xylene solubles were high, leading tomass polymerization of atactic polypropylene.

What is claimed is:
 1. A method of preparing a supported metallocenecatalyst, the method comprising the steps of: preparing a mixture of afirst compound of the following Chemical Formula 1 and a second compoundof the following Chemical Formula 2, wherein the first compound ofChemical Formula 1 and the second compound of Chemical Formula 2 are ina molar ratio of 1:1 to 3:1 in the mixture; adding toluene to themixture at a first temperature to dissolve the mixture; adding hexanethereto at a second temperature lower than the first temperature toobtain a resultant mixture; filtering the resultant mixture to remove asolidified compound of Chemical Formula 2; and removing the toluene andthe hexane from the filtered mixture to obtain a resulting product, andthen supporting the resulting product onto a carrier,

in Chemical Formulae 1 and 2, X¹ and X² are each independently halogen,R¹ and R^(1′) are each independently a tert-butyl-substituted phenylgroup, R², R³, R⁴, R^(2′), R^(3′), and R^(4′) are each independentlyhydrogen, an alkyl group having 1 to 20 carbon atoms, A is carbon,silicon, or germanium, and R⁵ and R⁶ are each independently an alkylgroup having 1 to 20 carbon atoms.
 2. The method of preparing asupported metallocene catalyst of claim 1, wherein R⁵ and R⁶ in ChemicalFormulae 1 and 2 are a methyl group.
 3. The method of preparing asupported metallocene catalyst of claim 1, wherein a weight ratio of thetoluene and the hexane used is 1:0.01 to 1:100.
 4. The method ofpreparing a supported metallocene catalyst of claim 1, wherein the stepof adding toluene the mixture is performed at a temperature of −78° C.to 70° C. for 1 hour to 128 hours.
 5. The method of preparing asupported metallocene catalyst of claim 1, wherein a concentration ofthe mixture in the combination of the toluene and the hexane is 0.05 Mto 2.0 M.
 6. The method of preparing a supported metallocene catalyst ofclaim 1, wherein the step of adding toluene to the mixture to dissolvethe mixture is performed at 30° C. to 70° C. for 0.1 hours to 3 hours,and the step of adding hexane thereto is performed at −30° C. to 30° C.for 6 hours to 96 hours.
 7. The method of preparing a supportedmetallocene catalyst of claim 1, wherein the step of adding toluene tothe mixture to dissolve the mixture and the step of adding hexanethereto are performed twice or more.
 8. The method of preparing asupported metallocene catalyst of claim 1, wherein the first compound ofChemical Formula 1 is represented by:

and the second compound of Chemical Formula 2 is represented by: